I live in kelowns-BC. And there is no law requiring you wear a helmet while riding a bicycle, regardless of age. In fact, Kelowna is one of only 3 provinces in the entire country where helmets aren't even required for bikes, or motorcycles!
In downtown BC, the only cyclists who are required to wear helmets are bike messengers--but they rarely do, and the law isn't enforced.
But even though there aren't any state laws requiring bicyclists to wear helmets, individual townships and villages may pass local ordinances that do!
Here's a link to the helmet laws in various states and localities:
http://www.helmets.org/mandator.htm
